---
layout: "default"
title: "Operator: prefix --"
description: "Swift documentation for the 'prefix --' operator."
root: "/v2.0"
---

<code class="language-swift">prefix operator prefix -- {
    associativity 
    precedence 
}</code>

<h3>Declarations</h3>

<div class="declaration" id="func-mnsmns-inout_-double">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-double">prefix func --(<wbr>inout: Double)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-double"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout rhs: Double) -&gt; Double</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-float">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-float">prefix func --(<wbr>inout: Float)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-float"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout rhs: Float) -&gt; Float</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-float80">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-float80">prefix func --(<wbr>inout: Float80)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-float80"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout rhs: Float80) -&gt; Float80</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-int">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-int">prefix func --(<wbr>inout: Int)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-int"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: Int) -&gt; Int</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-int8">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-int8">prefix func --(<wbr>inout: Int8)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-int8"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: Int8) -&gt; Int8</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-int16">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-int16">prefix func --(<wbr>inout: Int16)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-int16"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: Int16) -&gt; Int16</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-int32">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-int32">prefix func --(<wbr>inout: Int32)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-int32"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: Int32) -&gt; Int32</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-int64">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-int64">prefix func --(<wbr>inout: Int64)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-int64"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: Int64) -&gt; Int64</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-uint">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-uint">prefix func --(<wbr>inout: UInt)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-uint"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: UInt) -&gt; UInt</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-uint8">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-uint8">prefix func --(<wbr>inout: UInt8)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-uint8"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: UInt8) -&gt; UInt8</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-uint16">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-uint16">prefix func --(<wbr>inout: UInt16)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-uint16"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: UInt16) -&gt; UInt16</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-uint32">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-uint32">prefix func --(<wbr>inout: UInt32)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-uint32"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: UInt32) -&gt; UInt32</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-inout_-uint64">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-inout_-uint64">prefix func --(<wbr>inout: UInt64)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-inout_-uint64"><div class="p">
    

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --(inout x: UInt64) -&gt; UInt64</code>
    
    
</div></div>
</div>
<div class="declaration" id="func-mnsmns-t_-bidirectionalindextype-inout_-t">
<a class="toggle-link" data-toggle="collapse" href="#comment-func-mnsmns-t_-bidirectionalindextype-inout_-t">prefix func <wbr>-- &lt;T : BidirectionalIndexType&gt;(<wbr>inout: T)</a>
        
<div class="comment collapse" id="comment-func-mnsmns-t_-bidirectionalindextype-inout_-t"><div class="p">
    <p>Replace <code>i</code> with its <code>predecessor()</code> and return the updated value
of <code>i</code>.</p>

    <h4>Declaration</h4>    
    <code class="language-swift">prefix func --&lt;T : BidirectionalIndexType&gt;(inout i: T) -&gt; T</code>
    
    
</div></div>
</div>
